Continuous radiant furnace sintering machine



April 1963 H. T. STIRLING 3,083,956

CONTINUOUS RADIANT FURNACE SINTERING MACHINE Filed Dec. 31. 1957 3 Sheets-Sheet 1 INVENTOR. f/qkoL 0 7T SrJ/PL 1M6 April 2, 1963 H. T. STIRLING 3,

CONTINUOUS RADIANT FURNACE SINTERING MACHINE Filed Dec- 31. 1957 3 Sheets-Sheet 2 2.9 SECTION 26 2C BY I mam 9? Jul:

9 7- TO Eva/5 April 2, 1963 H. T. STIRLING 3,083,956

CONTINUOUS RADIANT FURNACE SINTERING MACHINE Filed Dec. 51, 1957 3 Sheets-Sheet 3 20 il- 11 J0 INVENTOR. 16/939040 7T \S'T-IELJMG iJite States atet G 3,083,956 CONTINUOUS RADIANT FURNACE SINTERKNG MACHINE Harold T. Stirling, littsburgh, Pa., assignor to Koppers Company, Inc., a corporation of Delaware Filed Dec. 31, 1957, Ser. No. 706,518 2 Claims. (Cl. 266-21) This invention relates in general to apparatus for sintering and heat hardening beds of solid material, and more particularly to improvements which promote uniform dis tribution of the heat and thus prevent hot spots in the sinter bed, in an apparatus of the continuous sinter strand type with a radiant type ignition furnace for tiring or heating the top of a bed on the strand of pallets as they pass continuously over a wind box for exhausting the gases from the alletbed.

More especiall the invention is directed to an improvement attaining this end in apparatus of this general type which heretofore have had for their main operating characteristic, a downwardly opening refractory lined radiant heat chamber with vertical walls, and arched roof parallel or transverse to the strand travel, and a row of fuel burner nozzles set in the brickwork of the exit walls of the furnace at an angle so that the direction of flame is countercurrcnt to the strand travel with the flame impinging on the bed and spreading out to cover a large area of the bed on the pallets as they pass under the ignition furnace.

In operation, such system is of particular advantage over non-radiant type continuous sinter strand furnace systems because with this radiant type system it is possible to operate by burning blast furnace gas, coke oven gas, or mixed blast furnace and coke oven gas, and in so doing considerabiy increasing the sintering per square foot of grate ares, dec the hot sinter returns to about onefourth, reduce dust in the discharge area considerably, strengthen and harden the top of the sinter bed, as well as reduce the amount of coke in the mix, and increase the blast furnace production considerably with a still better quality of sintcr produced by the use of this type of ignition burner over other types of non-radiant heating sintering furnaces.

A drawback to such system has been that the distribution of heat is not uniform and as a result hot spots are formed in the sinter bed due, apparently, to the arched formation of the roof of the furnace in conjunction with the angle of impingement of the flame on the bed by the burners to spread the flame out to cover a large area.

The primary aim of the present invention is the modification of this sintering furnace system in a manner to retain its aforesaid advantages while eliminating these disadvantages in a manner to promote uniform distribution of the heat from the burner nozzles, thus preventing hot spots in the sinter bed.

Accordingly, the present invention provides for the purpose a continuous sinter strand system with a radiant ignition furnace as aforesaid but having as a novel operating characteristic an entrance wall shortened relative to the exit wall of the furnace and a generally fiat roof inclined from the top of the exit wall down to the top of the entrance wall, so that the roof slopes downwardly in a direction countercurrent to the direction of the strand under the downwardly open mouth of the furnace chamber.

Another novel feature is that this radiant ignition furnace can be raised or lowered or put on a slope if desired while operating, in order to get optimum burning without shutting down.

With this change, the burner nozzles are still in the exit wall of the furnace at an angle to direct the flame into the furnace countercurrent to the strand travel, but the nozzles are set in the upper half of the exit wall of the furnace so as to have their axial centers at a level to impinge or project through the middle of the vertical height of the entrance wall of the housing rather than on to the bed on the strand, to spread out and cover a large area.

A system as thus devised has been in actual use and found performing in its expected superior manner for preventing hot spots in the bed while satisfactorily accomplishing the aforesaid advantages over non-radiant type continuous sinter strand furnace systems. The invention is not limited in all its aspects to sintering of ore as such, as above-described but is equally applicable to heat hardening other strand bed materials, such as fly ash, ferrous and non-ferrous material requiring pelletizing, in the form of green pellets or bailed fines, with and without admixture with fuels to provide the heat for hardening or fusing, as in the formation of lightweight aggregate.

In addition to the general objects recited above, the invention has for further objects such other improvements or advantages as may be found to obtain in the apparatus hereinafter-described and claimed.

In the accompanying drawings forming a part of this specification and showing, for purposes of illustration, the best mode of embodying and practicing the invention.

FIGURE 1 is a side elevational view of a continuous sinter strand apparatus with the novel furnace features therein;

FIGURE 2 is an enlarged vertical sectional view of the novel parts of FIGURE 1, the section being also on the line 2C-2C of FIGURE 3;

FIGURE 3 is front elevational view partly in section, taken on the lines 3B3B and 3A-3A of FIGURE 2.

Referring to the drawings:

There is shown a standard sintering machine of the continuous sinter strand type of the endless conveyor type comprising an upper strand 10, pallets 11, and a lower strand or run 12 mounted for rotation by means of sprocket wheels 13. In the upper run or strand the pallets ride along rails 14 by means of rollers 15 and return on rails 14'. Wind boxes 16 are arranged longitudinally below the upper strand 10, which as usual are provided with dust collecting hoppers 17 and are also connected to a stack through a gas line 18 as well as sealed by wear bars 19 and seal bars 20 in the conventional manner.

As shown on the drawings, the conveying strand 10 moves to the left and sinter mixture is fed to the pallets at a region to the right, in FIG. 2 and to the left in FIG. I, of the dead plate 21 by sinter mixture feed means in the form of a vibrating feeder pan 22 which deposits the mix evenly and gently on the pallets throughout the full width of the strand. Just before the feeder 22 a surge bin 23 is provided as a hearth layer feed means to lay down a hearth layer on the grate. The top of the bed 10 is ignited or, as with the present invention here, subjected to a first stage ignition at a region after the feeder 22 by means of a radiant type ignition furnace 24.

The prepared bed 1.0 travels under the furnace 24 and out over further wind boxes and is fully sintered by the time it reaches the discharge end of the machine at the left as shown on the drawings.

The structure thus far described is typical of this type of sintering plant and hence need not be described in further detail.

In previous practice, the furnace 24 generally consisted of an arc-shaped steel shell with a refractory lining comprising vertical walls and an arc-shaped roof paralleling or transverse to the line of travel of the upper run, with a row of burner nozzles 25 set in the brickwork in the exit wall 26 of the furnace with the angle of the burners fixed so that the direction of the flame is countercurrent to the strand travel, with the flame impinging on the bed and spreading out to cover a large area. In operation the operator aims to attain complete ignition across the bed and burns enough gas to obtain a black top while avoiding fusing of the surface of the bed to such an extent that bed permeability is disadvantageously affected.

Ignition time should be approximately one minute, depending on sintering plant operation. Therefore, if the sintering machine is long and can travel at a great rate of speed, for instance, 24 feet per minute, the furnace would be 24 feet x width of pallet or strand.

When the ignition furnace area is to be 24 feet x 12 feet, instead of having a single furnace 24 feet long, two of the radiant type furnaces, each as long as the width of the strand, preferably are used in th series.

In accordance with the present invention, the furnace 24 is constituted of a rectangular metallic framework 27 having a shorter refractory lined vertical entrance wall 28 composed of horizontal courses of refractory brick and a higher exit wall 26 of the same material, both mounted on water cooled lintels 29. The chamber space between said walls is unenclosed from their tops down forming a downwardly opening radiant heat chamber 30. The top of the chamber is closed off by a generally flat roof 31, downwardly inclined or sloped from the top of the exit wall 26 to the top of the entrance wall 28 and the two opposite sides of the chamber are closed off by vertical walls 32 formed of refractory brick in superposed horizontal courses supported by water cooled lintels 29 in the same manner as the vertical exit and entrance walls 26, 28. The furnace chamber area is as Wide as the strand and as long, in the direction of travel of the strand, as the width of the strand or upper run.

The inclined flat roof 31 is constituted of interlocked vertical tile in a single course which are suspended from a roof support 33 separate from the furnace frame support 34. Expansion joints 35 are provided for the inclined roof which is also provided with three thermocouple holes 36. The burner nozzles 25 are of the comb block type set in neck brick 27 in the upper half of the exit wall 26. These are fixed for firing at an angle, to have their longitudinal axes 38 on a line, or at level to project through, or impinge at, about the middl of the vertical height 39 of the vertical entrance wall 28. These nozzles 25 are fed with air through line 40 and gas through line 41 of flexible hose from air and gas headers (not shown). The gas may be either coke oven gas or blast furnace gas, or a mixture of these two gases.

The framework 27 is supported at the four corners of the furnace from the support 34 by four jacks in the form of a turn buckle pivotally connected at their tops to the framework 34 and likewise pivotally connected at their lower ends to the framework 27.

In operation the firing is effected at a rate in correspondence with that above-described with the same or better results, except that the distribution of heat is more uniform, flame impingement directly on the top of the bed 10 avoided, thus preventing hot spots in the sinter bed 10'. Rotation of the turnbuckles at the corners raises or lowers the furnace from and to the top of the bed on the upper strand.

The invention as hereinabove set forth is embodied in a particular form and manner but may be variously embodied Within the scope of the claims hereinafter made.

I claim:

1. Apparatus for continuous sinter bed radiant furnace heating, comprising: wind box means, a continuous strand of sinter pallets mounted for movement across the wind boxes of said means, means for continuously advancing the strand of pallets, hearth layer feed means to lay down a hearth protective layer on the strand of pallets, sinter mixture feed means for feeding sinter mixture to the bed after the hearth layer feed means, a downwardly opening refractory lined radiant heat chamber in position over the strand after the sinter mixture feed means for firing a bed on the strand and constituted of confrontmg vertical tall and shorter walls, a generally flat refractory roof on an incline from the top of the tail wall to tht top of the short wall, a fuel nozzle set in the upper half of the tall Wall and fixed at an angle in said tall wall to have the central axis of the nozzle at a level to project through the short wall above the base thereof and means to discharge the fuel so that its flame impinges on the short wall above the base thereof and avoids direct impringemerit of the flame on the sinter mixture, whereby the radiant heat from said chamber ignites said sinter mixture on said hearth layer.

2. Apparatus for continuous sinter bed radiant furnace heating, comprising: the combination with wind box means, a continuous sinter strand of pallets mounted for continuous movement across the wind boxes of said means, means for continuously advancing the sinter strand, of sinter mixture feed means for feeding sinter mixture to the bed, and a downwardly opening refractory lme radiant heat chamber in position over the sinter strand after the sinter mixture feed means for firing the top of a bed thereon, with confronting vertical refractory entrance and exit walls enclosed at the top by a refractory roof, and with fuel nozzles set in the exit wall and fixed at an angle to discharge flame into the chamber above the bed, characterized by said entrance wall being shorter than the exit wall, said roof being a generally flat one inclined downwardly from the top of the exit wall to the top of the entrance wall, said fuel nozzles being set in tht upper half of the exit wall at an angle fixed to have the central axes of the nozzles at a level to project through the middle of the vertical height of the exit wall and means to discharge the fuel so that its flame impinges on the short wall above the base thereof and avoids direct impmgemtnt of the flame on the sinter mixture, whereby the radiant heat from said chamber ignites said sinter mixture on said hearth layer.

References Cited in the file of this patent UNITED STATES PATENTS 916,397 Dwight Mar. 23, 1909 1,540,205 Cousin June 2, 1925 1,827,773 Beasley Oct. 20, 1931 1,984,747 Klencke Dec. 18, 1934 2,409,072 Shallock Oct. 8, 1946 2,750,272 Lellep June 12, 1956 FOREIGN PATENTS 318,197 Great Britain Feb. 27, 1930 

1. APPARATUS FOR CONTINUOUS SINTER BED RADIANT FURNACE HEATING, COMPRISING: WIND BOX MEANS, A CONTINUOUS STRAND OF SINTER PALLETS MOUNTED FOR MOVEMENT ACROSS THE WIND BOXES OF SAID MEANS, MEANS FOR CONTINUOUSLY ADVANCING THE STRAND OF PALLETS, HEARTH LAYER FEED MEANS TO LAY DOWN A HEARTH PROTECTIVE LAYER ON THE STRAND OF PALLETS, SINTER MIXTURE FEED MEANS FOR FEEDING SINTER MIXTURE TO THE BED AFTER THE HEARTH LAYER FEED MEANS, A DOWNWARDLY OPENING REFRACTORY LINED RADIANT HEAT CHAMBER IN POSITION OVER THE STRAND AFTER THE SINTER MIXTURE FEED MEANS FOR FIRING A BED ON THE STRAND AND CONSTITUTED OF CONFRONTING VERTICAL TALL AND SHORTER WALLS, A GENERALLY FLAT REFRACTORY ROOF ON AN INCLINE FROM THE TOP OF THE TAIL WALL TO THE TOP OF THE SHORT WALL, A FUEL NOZZLE SET IN THE UPPER HALF OF THE TALL WALL AND FIXED AT AN ANGLE IN SAID TALL WALL TO HAVE THE CENTRAL AXIS OF THE NOZZLE AT A LEVEL TO PROJECT THROUGH THE SHORT WALL ABOVE THE BASE THEREOF AND MEANS TO DISCHARGE THE FUEL SO THAT ITS FLAME IMPINGES ON THE SHORT WALL ABOVE THE BASE THEREOF AND AVOIDS DIRECT IMPINGEMENT OF THE FLAME ON THE SINTER MIXTURE, WHEREBY THE RADIANT HEAT FROM SAID CHAMBER IGNITES SAID SINTER MIXTURE ON SAID HEARTH LAYER. 